1. Field of the Invention
This invention relates to a reception interface unit in a transmission system for putting time series digital data into a data packet and transferring the data packet at high speed.
2. Description of the Related Art
IEEE1394-1995 standard has been proposed as an interface standard for transferring time series data of audio signals, video signals, etc., in a data packet at high speed between electric devices such as audio devices, video devices, computers, etc.
However, in a data transfer system based on the IEEE1394-1995 standard, it is conceivable that received digital data cannot be reproduced at proper timing over a considerable period of time in a receiving party because of a change in the reference time in the system, a malfunction, etc.
The present invention has been made to solve the above problem, and therefore an object of the invention is to provide a reception interface unit in a transmission system for enabling digital data sent by a transmitting party to be restored to a state in which the data can be reproduced immediately at proper timing in a receiving party.
To achieve the above object, according to a first aspect of the invention, there is provided a reception interface unit in a transmission system wherein time series data is divided into data groups and a data packet comprising reproduction specification time data specifying the time at which each data piece in the data groups should be reproduced, added to the data groups is transmitted on a transmission bus in a time division manner, the reception interface unit comprising a cycle timer for counting the reference time of a home device based on the reference time on the transmission bus, reproduction specification time data extraction means for extracting the reproduction specification time data in the data groups from a signal received via the transmission bus and storing the reproduction specification time data in a buffer, a reception buffer for inputting and storing the data pieces in the data groups in order and reading out the data pieces in the storage order in response to a reproduction clock, a match detection means for generating a reference clock pulse if the reference time of the home device matches the reproduction specification time, and a PLL circuit being responsive to the reference clock pulse for generating a clock signal which is phase synchronized with the reference clock pulse as the reproduction clock, wherein when the reference time on the transmission bus changes, the data stored in the buffer in the reproduction specification time data extraction means and the data stored in the reception buffer are all deleted.
According to a second aspect of the invention, there is provided a reception interface unit in a transmission system wherein time series data is divided into data groups and a data packet comprising reproduction specification time data specifying the time at which each data piece in the data groups should be reproduced, added to the data groups is transmitted on a transmission bus in a time division manner, the reception interface unit comprising a cycle timer for counting the reference time of the home device based on the reference time on the transmission bus, the cycle timer having at least two registers for temporarily storing the reference time of the home device before the reference time on the transmission bus changes and the reference time of the home device after the reference time on the transmission bus changes, reproduction specification time data extraction means for extracting the reproduction specification time data in the data groups from a signal received via the transmission bus and storing the reproduction specification time data in a buffer, a reception buffer for inputting and storing the data pieces in the data groups in order and reading out the data pieces in the storage order in response to a reproduction clock, a match detection means for generating a reference clock pulse if the reference time of the home device matches the reproduction specification time, and a PLL circuit being responsive to the reference clock pulse for generating a clock signal which is phase synchronized with the reference clock pulse as the reproduction clock, characterized in that when the buffer becomes empty of the data stored before the reference time on the transmission bus changes, either or both of the reproduction specification time data extraction means and the reception buffer output a control signal, that when the reference time on the transmission bus changes, the reproduction specification time data extraction means and the reception buffer interrupt write of the data and when each buffer becomes empty of the data stored before the reference time on the transmission bus changes, restarts write of the data, and that the cycle timer changes the reference time of the home device from the reference time of the home device before the reference time on the transmission bus changes to that after the reference time on the transmission bus changes based on the control signal and outputs the reference time of the home device to the match detection circuit.
According to a third aspect of the invention, there is provided a reception interface unit in a transmission system wherein time series data is divided into data groups and a data packet comprising reproduction specification time data specifying the time at which each data piece in the data groups should be reproduced, added to the data groups is transmitted on a transmission bus in a time division manner, the reception interface unit comprising a cycle timer for counting the reference time of the home device based on the reference time on the transmission bus, reproduction specification time data extraction means for extracting the reproduction specification time data in the data groups from a signal received via the transmission bus and storing the reproduction specification time data in a buffer, a reception buffer for inputting and storing the data pieces in the data groups in order and reading out the data pieces in the storage order in response to a reproduction clock, a match detection means for generating a reference clock pulse if the reference time of the home device matches the reproduction specification time, and a PLL circuit being responsive to the reference clock pulse for generating a clock signal which is phase synchronized with the reference clock pulse as the reproduction clock, characterized in that when the reference time on the transmission bus changes, the reproduction specification time data extraction means deletes all the reproduction specification time data stored in the buffer.
According to a fourth aspect of the invention, there is provided a reception interface unit in a transmission system wherein time series data is divided into data groups and a data packet comprising reproduction specification time data specifying the time at which each data piece in the data groups should be reproduced, added to the data groups is transmitted on a transmission bus in a time division manner, the reception interface unit comprising a cycle timer for counting the reference time of the home device based on the reference time on the transmission bus, reproduction specification time data extraction means for extracting the reproduction specification time data in the data groups from a signal received via the transmission bus and storing the reproduction specification time data in a buffer, dummy reproduction specification time data generation means for generating dummy reproduction specification time data from the reproduction specification time data extracted in the reproduction specification time data extraction means, selection means for selectively outputting either of the reproduction specification time data from the reproduction specification time data extraction means and the dummy reproduction specification time data from the dummy reproduction specification time data generation means, a reception buffer for inputting and storing the data pieces in the data groups in order and reading out the data pieces in the storage order in response to a reproduction clock, a match detection means for generating a reference clock pulse if the reference time of the home device matches the reproduction specification time output from the selection means, and a PLL circuit being responsive to the reference clock pulse for generating a clock signal which is phase synchronized with the reference clock pulse as the reproduction clock, characterized in that the selection means selects the reproduction specification time data from the reproduction specification time data extraction means before the reference time on the transmission bus changes and selects the dummy reproduction specification time data from the dummy reproduction specification time data generation means after the reference time on the transmission bus changes.
According to a fifth aspect of the invention, the reception interface unit as set forth in the fourth aspect of the invention further includes subtraction means for finding a difference between the reproduction specification time data extracted in the reproduction specification time data extraction means just before the reference time on the transmission bus changes and the reproduction specification time data extracted in the reproduction specification time data extraction means just after the reference time changes and outputting the found time difference to the dummy reproduction specification time data generation means, wherein when the reference time on the transmission bus changes, the dummy reproduction specification time data generation means adds the time difference to the reproduction specification time data stored in the buffer in the reproduction specification time data extraction means before the reference time changes to generate dummy reproduction specification time data.
According to a sixth aspect of the invention, in the invention of the fourth or fifth aspect, when the buffer becomes empty of the data stored before the reference time on the transmission bus changes, either or both of the reproduction specification time data extraction means and the reception buffer output a control signal, and the selection means selects the reproduction specification time data from the reproduction specification time data extraction means based on the control signal.
According to a seventh aspect of the invention, there is provided a reception interface unit in a transmission system wherein time series data is divided into data groups and a data packet comprising reproduction specification time data specifying the time at which each data piece in the data groups should be reproduced, added to the data groups is transmitted on a transmission bus in a time division manner, the reception interface unit comprising a cycle timer for counting the reference time of the home device based on the reference time on the transmission bus, reproduction specification time data extraction means for extracting the reproduction specification time data in the data groups from a signal received via the transmission bus and storing the reproduction specification time data in a buffer, a reception buffer for inputting and storing the data pieces in the data groups in order and reading out the data pieces in the storage order in response to a reproduction clock, a match detection means for generating a reference clock pulse if the reference time of the home device matches the reproduction specification time, dummy reference clock pulse generation means for generating a dummy reference clock pulse based on the period of the reference clock pulse, selection means for selectively outputting either the dummy reference clock pulse from the dummy reference clock pulse generation means and the reference clock pulse from the match detection means, and a PLL circuit being responsive to the reference clock pulse for generating a clock signal which is phase synchronized with the reference clock pulse as the reproduction clock, characterized in that the selection means selects the reference clock pulse from the match detection means before the reference time on the transmission bus changes and selects the dummy reference clock pulse from the dummy reference clock pulse generation means after the reference time on the transmission bus changes.
According to an eighth aspect of the invention, in the invention of the seventh aspect, the dummy reference clock pulse generation means has a counter for measuring the period of the reference clock pulse and generates the dummy reference clock pulse based on the measurement value.
According to a ninth aspect of the invention, in the invention of the seventh or eighth aspect, when the buffer becomes empty of the data stored before the reference time on the transmission bus changes, either or both of the reproduction specification time data extraction means and the reception buffer output a control signal, and the selection means selects the reference clock pulse from the match detection means based on the control signal.
According to a tenth aspect of the invention, there is provided a reception interface unit in a transmission system wherein time series data is divided into data groups and a data packet comprising reproduction specification time data specifying the time at which each data piece in the data groups should be reproduced, added to the data groups is transmitted on a transmission bus in a time division manner, the reception interface unit comprising a cycle timer for counting the reference time of the home device based on the reference time on the transmission bus, the cycle timer having at least two registers for temporarily storing the reference time of the home device before the reference time on the transmission bus changes and the reference time of the home device after the reference time on the transmission bus changes, reproduction specification time data extraction means for extracting the reproduction specification time data in the data groups from a signal received via the transmission bus and storing the reproduction specification time data, a reception buffer for inputting and storing the data pieces in the data groups in order and reading out the data pieces in the storage order in response to a reproduction clock, a match detection means for generating a reference clock pulse if the reference time of the home device matches the reproduction specification time, and a PLL circuit being responsive to the reference clock pulse for generating a clock signal which is phase synchronized with the reference clock pulse as the reproduction clock, characterized in that the cycle timer outputs the reference time of the home device stored before the reference time on the transmission bus changes for the data stored in the reproduction specification time data extraction means and the reception buffer before the reference time on the transmission bus changes and outputs the reference time of the home device stored after the reference time on the transmission bus changes for the data stored in the reproduction specification time data extraction means and the reception buffer after the reference time on the transmission bus changes.
According to an eleventh aspect of the invention, the reception interface unit as set forth in the tenth aspect of the invention further includes subtraction means for finding a time difference between reproduction specification time data output from the reproduction specification time data extraction means and reproduction specification time data output from the reproduction specification time data extraction means immediately preceding that reproduction specification time data and a determination circuit for determining whether reproduction specification time data is reproduction specification time data stored before or after the reference time on the transmission bus changes based on the time difference found by the subtraction means, wherein the cycle timer is responsive to the determination result of the determination circuit for selectively outputting the reference time of the home device before the reference time on the transmission bus changes or the reference time of the home device after the reference time on the transmission bus changes to the match detection circuit.
According to a twelfth aspect of the invention, in the invention as set forth in the eleventh aspect, when the buffer becomes empty of the data stored before the reference time on the transmission bus changes, either or both of the reproduction specification time data extraction means and the reception buffer output a control signal, and the cycle timer selectively outputs the reference time of the home device before the reference time on the transmission bus changes or the reference time of the home device after the reference time on the transmission bus changes to the match detection circuit based on the control signal.
In the first aspect of the invention, when the reference time on the transmission bus changes, the data stored in the buffer in the reproduction specification time data extraction means and the data stored in the reception buffer are all deleted. Thus, after the reference time on the transmission bus changes, the digital data after the reference time changes can be reproduced immediately at proper timing in the receiving party.
In the second aspect of the invention, when the buffer becomes empty of the data stored before the reference time on the transmission bus changes, either or both of the reproduction specification time data extraction means and the reception buffer output a control signal, when the reference time on the transmission bus changes, the reproduction specification time data extraction means and the reception buffer interrupt write of the data and when each buffer becomes empty of the data stored before the reference time on the transmission bus changes, restart write of the data, and the cycle timer changes the reference time of the home device from the reference time of the home device before the reference time on the transmission bus changes to that after the reference time on the transmission bus changes based on the control signal and outputs the reference time of the home device to the match detection circuit. Thus, in the receiving party, after the reference time on the transmission bus changes, the digital data before the reference time on the transmission bus changes can be reproduced immediately at proper timing and then subsequently the digital data after the reference time on the transmission bus changes can be reproduced.
In the third aspect of the invention, when the reference time on the transmission bus changes, the reproduction specification time data extraction means deletes all the reproduction specification time data stored in the buffer. Thus, after the reference time on the transmission bus changes, the digital data before and after the reference time on the transmission bus changes can be reproduced immediately at proper timing in the receiving party.
In the fourth aspect of the invention, the selection means selects the reproduction specification time data from the reproduction specification time data extraction means before the reference time on the transmission bus changes and selects the dummy reproduction specification time data from the dummy reproduction specification time data generation means after the reference time on the transmission bus changes.
In the fifth aspect of the invention, the reception interface unit further includes subtraction means for finding a difference between the reproduction specification time data extracted in the reproduction specification time data extraction means just before the reference time on the transmission bus changes and the reproduction specification time data extracted in the reproduction specification time data extraction means just after the reference time on the transmission bus changes and outputting the found time difference to the dummy reproduction specification time data generation means, wherein when the reference time on the transmission bus changes, the dummy reproduction specification time data generation means adds the time difference to the reproduction specification time data stored in the buffer in the reproduction specification time data extraction means before the reference time on the transmission bus changes to generate dummy reproduction specification time data.
In the sixth aspect of the invention, when the buffer becomes empty of the data stored before the reference time on the transmission bus changes, either or both of the reproduction specification time data extraction means and the reception buffer output a control signal, and the selection means selects the reproduction specification time data from the reproduction specification time data extraction means based on the control signal. Thus, after the reference time on the transmission bus changes, the digital data before and after the reference time on the transmission bus changes can be reproduced immediately at proper timing in the receiving party.
In the seventh aspect of the invention, the selection means selects the reference clock pulse from the match detection means before the reference time on the transmission bus changes and selects the dummy reference clock pulse from the dummy reference clock pulse generation means after the reference time on the transmission bus changes.
In the eighth aspect of the invention, the dummy reference clock pulse generation means has a counter for measuring the period of the reference clock pulse and generates the dummy reference clock pulse based on the measurement value.
In the ninth aspect of the invention, when the buffer becomes empty of the data stored before the reference time on the transmission bus changes, either or both of the reproduction specification time data extraction means and the reception buffer output a control signal, and the selection means selects the reference clock pulse from the match detection means based on the control signal. Thus, after the reference time on the transmission bus changes, the digital data before and after the reference time on the transmission bus changes can be reproduced immediately at proper timing in the receiving party.
In the tenth aspect of the invention, the cycle timer outputs the reference time of the home device stored before the reference time on the transmission bus changes for the data stored in the reproduction specification time data extraction means and the reception buffer before the reference time on the transmission bus changes and outputs the reference time of the home device stored after the reference time on the transmission bus changes for the data stored in the reproduction specification time data extraction means and the reception buffer after the reference time on the transmission bus changes.
In the eleventh aspect of the invention, the reception interface unit further includes subtraction means for finding a time difference between reproduction specification time data output from the reproduction specification time data extraction means and reproduction specification time data output from the reproduction specification time data extraction means immediately preceding that reproduction specification time data and a determination circuit for determining whether reproduction specification time data is reproduction specification time data stored before or after the reference time on the transmission bus changes based on the time difference found by the subtraction means, wherein the cycle timer is responsive to the determination result of the determination circuit for selectively outputting the reference time of the home device before the reference time on the transmission bus changes or the reference time of the home device after the reference time on the transmission bus changes to the match detection circuit.
In the twelfth aspect of the invention, when the buffer becomes empty of the data stored before the reference time on the transmission bus changes, either or both of the reproduction specification time data extraction means and the reception buffer output a control signal, and the cycle timer selectively outputs the reference time of the home device before the reference time on the transmission bus changes or the reference time of the home device after the reference time on the transmission bus changes to the match detection circuit based on the control signal. Thus, after the reference time on the transmission bus changes, the digital data before and after the reference time on the transmission bus chalnges can be reproduced immediately at proper timing in the receiving party.